Vox Tts

vox-tts

A self-hosted TTS service at https://vox.delo.sh wrapping VoxCPM2 with a postgres-backed voice profile store and support for multiple engines. Deployed at ~/docker/stacks/utils/vox/.

Quick reference

Trailing slash on /mcp/ is mandatory. Without it, FastAPI 307-redirects and HTTPX drops the POST body.

speak vs speak_url: pick the right one

Default to speak_url. It costs the agent nothing in tokens (the response is small JSON) and works across every delivery surface except raw inline byte processing.

Engine fallback

GET /healthz reports which engines are registered and whether each is available:

{
  "status": "ok",
  "model_loaded": true,
  "engines": [
    { "name": "voxcpm", "available": true },
    { "name": "elevenlabs", "available": true }
  ]
}

The orchestrator tries them in order. Every speak_url / speak response includes engine: "voxcpm" or engine: "elevenlabs" so you can detect when fallback engaged. ElevenLabs auto-disables when ELEVENLABS_API_KEY is unset.

Per-voice ElevenLabs mapping lives in the voices.elevenlabs_voice_id column. NULL falls back to the global default (ELEVENLABS_DEFAULT_VOICE, Adam by default).

Two modes: design vs cloning

The service supports two distinct approaches to voice selection. Pick the right one for the task.

Voice design (no reference audio)

Embed a parenthetical description at the start of the text. No voice profile needed. Fast, infinitely variable, great for one-offs or prototypes.

{ "text": "(A young woman with a gentle, melancholic tone)Hello, old friend." }

Reach for this when: the user wants a specific vibe/accent/emotion but doesn't need repeatability, or there's no reference clip handy.

See references/voice_design.md for the description pattern cookbook.

Voice cloning (reference audio)

Pass voice: "<name>" to use a saved profile. Repeatable, consistent across sessions. Seeded voice is rick.

{ "text": "Wubba lubba dub dub", "voice": "rick" }

Use this when: a named character/persona needs to persist across calls, or the user explicitly supplied a reference sample.

Rule of thumb: try description first unless the user names a voice or provides audio. Descriptions cost nothing to iterate.

Workflows

Add a new voice

Use scripts/add_voice.sh for a single command that uploads and registers the profile. The service auto-trims to 30s mono on ingest.

scripts/add_voice.sh <name> "<Display Name>" <path/to/audio.ext> [tag1,tag2]

Accepts wav, ogg, mp3, flac, m4a. For the raw HTTP form:

curl -X POST https://vox.delo.sh/voices \
  -F name=<slug> -F display_name="<Display>" \
  -F tags="<tag1>,<tag2>" \
  -F audio=@/path/to/audio.ogg

To also pin an ElevenLabs fallback voice, update the row directly against the host postgres:

psql -h localhost -U "$DEFAULT_USERNAME" -d vox -c \
  "UPDATE voices SET elevenlabs_voice_id='<voice_id>' WHERE name='<slug>';"

Synthesize speech (inline bytes)

scripts/synth.sh "Text to say" [voice] [output.wav]

Synthesize speech (delivery URL)

scripts/synth_url.sh "Text to say" [voice]
# prints the OGG/Opus URL to stdout; usable in Telegram/HA/curl

Send a voice note to Telegram (OpenClaw)

The end-to-end pattern for every OpenClaw agent. Two steps:

1. vox:speak_url(text, voice?)  →  { audio_url, engine, duration_s }
2. openclaw message send --channel telegram
                         --target <chat_id>
                         --media <audio_url>
                         --as-voice

Telegram fetches the URL directly from vox.delo.sh/audio/<uuid>.ogg (cached 1h). The agent never streams bytes. Works identically from crons, subagents, or direct agent turns.

See references/integrations.md for the full Telegram recipe, including per-job delivery config for cron jobs and topic-scoped sends.

Register with an MCP-capable agent

The service exposes FastMCP at /mcp/ with three tools: speak, speak_url, and list_voices_tool. Same endpoint works for Hermes, OpenClaw, and Claude Code.

scripts/register_mcp.sh hermes     # or openclaw, claude-code

See references/integrations.md for the exact config per agent, including the Hermes v0.8.0 CLI workaround.

Integrate with Node-RED

Drop-in custom node at ~/docker/stacks/utils/vox/node-red-contrib-vox/. Install into a running Node-RED:

cd ~/.node-red
npm install ~/docker/stacks/utils/vox/node-red-contrib-vox
# Restart Node-RED

Drag the vox tts node into a flow. Input msg.payload = string. Output msg.payload = WAV Buffer. Optional msg.voice overrides the configured voice.

See references/integrations.md Node-RED section for flow examples.

Integrate with a new platform (generic checklist)

When bolting vox onto any new CLI or platform, follow the universal integration checklist in references/integrations.md. Short version:

1. Does the target speak MCP? Register https://vox.delo.sh/mcp/ and use speak_url.
2. Else, does it accept an audio URL (Telegram, Discord, HA, <audio>)? POST /synthesize-url, hand over audio_url.
3. Else, does it accept bytes? POST /synthesize, stream WAV.
4. Else, does it run Node.js? Install node-red-contrib-vox or copy the wrapper.

Troubleshoot

Known failure modes and fixes live in references/troubleshooting.md. Check there before debugging from scratch. Top categories:

• OOM / VRAM exhaustion (usually reference audio too long or ollama coexistence)
• MCP handshake 400 (trailing slash missing on client-side URL)
• Telegram rejects the voice URL (use speak_url, not speak + upload; ensure OGG/Opus, not WAV)
• 500 on first request after container restart (warmup still in progress; ~45-60s with VOX_OPTIMIZE=1)
• Fallback engine not engaging (ELEVENLABS_API_KEY unset in container env)

Defaults cheat sheet

Steady-state synthesis ~2s on an RTX 3090 with VOX_OPTIMIZE=1. First call after restart takes ~15s (JIT compile). OGG/Opus transcode adds <100ms via ffmpeg.